This is an on-line discussion forum called Operating systems and old software.
The contents frame shows the titles of all articles posted to the discussion. Selecting a title will cause the corresponding article to be loaded into this frame.
You may also:
|Post a new article (starting a new thread)|
|Search the articles for a word or pattern|
In addition, each article has links to let you reply to it (continue the thread) and navigate the article list.